1. CRFS Technical Meeting LC Operations Update March 29, 2011

2. Topics Operations Update Research Efforts –Real Time Evaporation –Development of streamflow projections –Comparison of streamflow projections and operational impacts Probabilistic Mid-Term Operations Model

3. 24- Month Study Projected Powell WY Unreg Inflow Projected Powell Apr- Jul Unreg Inflow Projected Lake Powell EOWY Elevation w/ 8.23 maf Release Projected Glen Canyon WY Release Projected Amount of EQ Release Projected Lake Mead EOWY Elevation Probability of EQ Jan 2010 110% 13.2 maf 120% 9.5 maf 3663.31 ft11.36 maf3.13 maf1105.00 ft76% Feb 2010 105% 12.6 maf 113% 9.0 maf 3657.85 ft11.48 maf3.25 maf1105.00 ft71% Mar 2010 105% 12.7 maf 116% 9.2 maf 3658.16ft11.63 maf3.40 maf1105.00 ft97% Summary of Lake Powell and Lake Mead Operations Review of 24-Month Study 2011 Water Year Projections In 2011, the Equalization Elevation is 3643 ft.

4. 895 3,643 3,575 3,370 1,220 25.877 maf 0.0 maf 2.0 maf Dead Storage 1.9 maf Dead Storage 0.0 maf 9.5 maf Lake Powell Lake Mead Published March 2011 Projection for September 30, 2011 Equalization Elevation 3,700 24.322 maf Not to Scale 3632.49 Feet 1105.00 Feet Apr-Jul Forecast = 9.2 MAF (116% Average) 11.63 MAF 1,10511.9 maf

5. End of Water Year 2011 Lake Mead elevation end of WY 2011: 1105.00 feet Downstream water use during CY2011 has been lower than expected January storms and flooding along the Virgin River resulted in an initial increase to Lake Mead’s elevation of approximately 1.5 – 2.0 feet Since January, dry conditions have persisted in the Southwest

6. Lower Basin Side Inflows Glen Canyon to Hoover in WY/CY 2011 1,2 Month in WY/CY 2011 Total Intervening Flow Glen Canyon to Hoover (KAF) Total Intervening Flow Glen Canyon to Hoover (% of Average) Difference From 5-Year Average (KAF) HISTORYHISTORY October 201080145%+25 November 20101324%-41 December 2010248435%+191 January 20117599% February 20118491%-8 PROJECTEDPROJECTED March 201180 April 201160 May 201149 June 201123 July 201150 August 2011109 September 201170 October 201159 November 201148 December 201199 WY11 Totals941121%+166 CY11 Totals80699%-9 1 Values were computed with the LC’s gain-loss model for the 24-month study 2 Percent of average are based on the 5-year mean from 2005-2009 in CY 2010 and the 5-year mean from 2006-2010 in CY 2011.

7. Water Year 2011 Projected Operations August 2010 Most Probable 24-Month Study projected Lake Mead elevation on Jan 1, 2010 to be 1086.38 feet ICS Surplus Condition to govern Lake Mead operations Mexico deliveries may be reduced –Minute 318 signed to allow Mexico to store up to 260 KAF through 2013

9. Real Time Evaporation At Lake Mead 5-Year cooperative project with the USGS Measure and obtain hourly evaporation rates (and other parameters) from Lake Mead Develop new monthly coefficients for use in long-term modeling efforts Maintain program into the future

10. Comparison to Evaporation Rates in 24 Month Study Month 24-Month Study Calculated Evaporation (KAF) Measured Evaporation from USGS (KAF)* Difference (KAF) February 2010301119 March 2010332013 April 2010412318 May 2010473314 June 2010552134 July 2010683038 August 2010723438 September 2010593227 October 201042339 November 201039309 December 2010301119 January 2011990 February 20111015-5 *provisional

11. Impacts Will reduce error associated with 24-Month Study side inflow to Lake Mead term Since February 2010, side inflows would have been lower than previously calculated, most of the time Lower Basin is actively working with CBRFC to forecast side inflows as well Would like to keep project going, perhaps investigate bank storage

12. Recent Research Efforts Forced CBRFC RFS model with BCSD climate dataset through 2099 –10-15% decrease in flows over Gunnison and San Juan River Basins –8% increase in flows over Green River Basin Compared impacts of streamflow projections derived using VIC and RFS to operations over the San Juan –RFS flows generally lower over water year –Seasonal RFS flows above Navajo are higher

13. Development of New Probabilistic Mid- Term Operations Model Motivation is to better quantify range of uncertainty associated with mid-term operations forecasts Being developed by CADSWES graduate student in collaboration with Reclamation’s Modeling Work Group Developed in parallel with the 24-Month Study model Simulation horizon of 2-10 years Input is range of probable inflows –First and part of second year based on CBRFC’s ESP forecasts –On-going research to develop forecasting techniques beyond 2 years (being done by student developing model) Results expressed in probabilistic terms Target end of 2011 for first version of completed model

14. Lower Colorado River Operations For further information: http://www.usbr.gov/lc/region